1. Field of the Invention
The present invention relates to an apparatus and method for controlling the operation of a multiple speed heat pump system for supplying cooling and heating to an enclosure. More particularly, the present invention relates to the specific circuitry and method of staging multiple speed operation and in ascertaining under what conditions the various modes of operation should be selected for a heat pump system.
2. Description of the Prior Art
Two-speed compressors have been known in the art and utilized with refrigeration equipment to provide for staged capacity control. Most of these prior uses have involved heavy industrial and commercial equipment and only recently has the residential market been involved with multiple speed compressors. The control circuit claimed herein is specifically designed to be utilized with a two speed compressor having auxiliary electrical heat as part of the heating and cooling system for use in a residential enclosure. The claimed invention herein is not to be limited to residential use but finds like applicability in other types and forms of staged compressor refrigeration systems.
Typical of the prior art in this area is U.S. Pat. No. 3,978,382 issued to Pfarrer et al entitled "Control Apparatus for Two-Speed Single Phase Compressor". Therein a combination mechanical and electrical interlock is utilized to assure that the compressor is operating at either high speed or low speed and not a combination of both. This patent discloses a partial control system incorporating this combination mechanical-electrical interlock. The 3,978,382 patent does not however disclose the various controls for deciding which mode of operation should be utilized to most efficiently provide heating or cooling to the enclosure to be conditioned. This patent is more generally directed toward internal protection devices for the two speed compressor and the combination electrical mechanical interlock. U.S. Pat. No. 4,041,542 discloses a similar system for use with the three phase power supply. Again, there is no specific disclosure of incorporating the various control mechanisms into the control system of the unit to select the appropriate modes of operation.
The control circuit as described herein provides for phased speed operation dependent upon the heating demand sensed within the enclosure, upon the outdoor temperature and upon the mode of operation of the unit. Electrical resistance heaters are also staged into this system to provide additional heating under the appropriate weather conditions.